All Debut and Xpression models have a motor suspended by a rubber band – similar to how you'd suspend a sensitive microphone in a recording studio.
The idea is to isolated the motor from the turntable plinth so any rumble it generates from rotating isn't picked up by the turntable and amplified by your hi-fi system.
To stop the motor falling out during transport, these models are fitted with transport screws (shown by the red arrows below).
These screws can be completely removed. However, if your turntable isn't completely level or if the local power isn't very clean – the best policy is to only adjust the screws if you're noticing a problematic level of rumbling coming from the motor.
Completely removing the screws on a current Pro-Ject model can actually increase rumble, since it can put the motor out of vertical alignment.
In fact, you can get the best result from loosening the screws by a half to full turn, hence reducing coupling between the motor and the platter without letting the motor loose.
Easy as! Sometimes, the smallest mod gives the biggest result!
If you'd like to investigate more products that can help isolate your turntable from the perils of the outside world, we recommend you start with the Damp-It (pack of 4).